2012 Yukon xl 4x4 eating antifreeze?

[lifeisamystery]

Let me start off with the fact that she runs perfectly. She's got the 5.3, no hiccups, no codes, no rough idle, live stream on the scanner shows no reds, etc. I have a generic scanner, but it's able to do almost everything a dealer scanner can do.

She's got 275k miles on her and she purrs like a kitten with all the get up and go of a good beastie

THAT BEING SAID

After our 2500 mile cross country trip hauling 7 people, all their crap and a 4klb trailer (all out we weighed just over 11k lbs, yes I know, well over her limit, but we didn't have much of a choice, so we took it easy and kept a close watch on her and her fluids, etc.) she has started going through about a qt of 5w30 full synthetic every month, and about a gallon of coolant over 3 months. Oil looks good, she could use an oil change, but there are no particulates, and it's not milky at all. Using dexos coolant, no leaks of any kind, anywhere in or under the rig. No oil buildup of any kind anywhere in the bay or under the rig, and trust me, I'm skinny, I've crawled all over her and checked. The other thing she's started to do is rev up and down at stop lights. Nothing extreme, she goes back and forth from 600-1200, but that's only at an idle, doesn't matter if I'm in drive or neutral.

SO, my question is this: Should I be concerned about the disappearing fluids, or is this simply the symptom of an a high mileage motor? Normally I wouldn't be concerned about the oil consumption in an older rig, but the addition of the disappearing coolant has me wondering. I've driven and kept up on high mileage vehicles all my life, and the coolant thing is a new one on me with no apparent leaks. I don't have access to a pressure tester, so unfortunately I can't help there.

Any help, advice or experience is greatly appreciated

 

[donjetman]

Send an oil sample to a lab and have it analyzed.

 

[Fless]

If it's burning the coolant, your cats -- the precious metal ones -- will run out of their nine lives sooner than later.

 

[lifeisamystery]

If it's burning the coolant, your cats -- the precious metal ones -- will run out of their nine lives sooner than later.

I did smell cat a few times, but that was months ago and it hasn't happened since. What would happen if the cat found a new home?

 

[j91z28d1]

do as said above, send oil sample.

these things do have a history of posts around here of hard to find coolent leaks, they can seep so slowly it drys before you see it. usually it's the plastic T's by the fire wall or the radiator end tanks, you can't really see it till you pull to replace. if it's original, it's passed do anyways.


the fluctuating idle is concerning. normally I'd say vac leak, but don't know I've heard of one of these without a cam with rolling idle. hopefully it's not a crack somewhere it shouldn't be. that oil sample will tell you a lot.


do you have afm active? do you have a catch can? all of these benefit from a 30$ catch can.

 

[lifeisamystery]

do as said above, send oil sample.

these things do have a history of posts around here of hard to find coolent leaks, they can seep so slowly it drys before you see it. usually it's the plastic T's by the fire wall or the radiator end tanks, you can't really see it till you pull to replace. if it's original, it's passed do anyways.


the fluctuating idle is concerning. normally I'd say vac leak, but don't know I've heard of one of these without a cam with rolling idle. hopefully it's not a crack somewhere it shouldn't be. that oil sample will tell you a lot.


do you have afm active? do you have a catch can? all of these benefit from a 30$ catch can.

I don't currently park over a catch can, but it's something I'll do for a while to see what I find. I park over white gravel, have for months with no discoloration of any kind. As for the afm, I may be mistaken, but I don't believe mine has it. It's got the 6 speed tranny as well. It may be that the previous owner has the afm deleted, because there is absolutely no change whatsoever at cruising speed and no indication of any kind that it's switching down to 4 cyl mode. I'll see about the oil sample though.

 

[j91z28d1]

I don't currently park over a catch can, but it's something I'll do for a while to see what I find. I park over white gravel, have for months with no discoloration of any kind. As for the afm, I may be mistaken, but I don't believe mine has it. It's got the 6 speed tranny as well. It may be that the previous owner has the afm deleted, because there is absolutely no change whatsoever at cruising speed and no indication of any kind that it's switching down to 4 cyl mode. I'll see about the oil sample though.

a catch can is a small can that mount between the valve cover oil source and the intake vacuum. the air flows over a mesh inside, the oil sticks to it and drains down into the bottom to remove. there's a bunch of threads about it on here. it works, I consider my engine to be pretty tight and it still collects more than expected and that's all oil not being dumped into the intake ports. it might help with your oil usage. it's said as they burn the pvc system oil for years the piston rings develop build up and don't seal as well, using even more oil from the other side.


I never remember what got afm and what didn't. if it was activate I was going to say around here most believe it can contribute to your oil usage too. good that you don't see it say 4cyl mode on the dash.

 

[swathdiver]

Any help, advice or experience is greatly appreciated

Inspect all of the spark plugs. If she was turning over 3,000 rpms a lot on that trip, she'll go through a bit of oil. Check out all the cooling system tanks and lines and look for small leaks.

 

[Geotrash]

Let me start off with the fact that she runs perfectly. She's got the 5.3, no hiccups, no codes, no rough idle, live stream on the scanner shows no reds, etc. I have a generic scanner, but it's able to do almost everything a dealer scanner can do.

She's got 275k miles on her and she purrs like a kitten with all the get up and go of a good beastie

THAT BEING SAID

After our 2500 mile cross country trip hauling 7 people, all their crap and a 4klb trailer (all out we weighed just over 11k lbs, yes I know, well over her limit, but we didn't have much of a choice, so we took it easy and kept a close watch on her and her fluids, etc.) she has started going through about a qt of 5w30 full synthetic every month, and about a gallon of coolant over 3 months. Oil looks good, she could use an oil change, but there are no particulates, and it's not milky at all. Using dexos coolant, no leaks of any kind, anywhere in or under the rig. No oil buildup of any kind anywhere in the bay or under the rig, and trust me, I'm skinny, I've crawled all over her and checked. The other thing she's started to do is rev up and down at stop lights. Nothing extreme, she goes back and forth from 600-1200, but that's only at an idle, doesn't matter if I'm in drive or neutral.

SO, my question is this: Should I be concerned about the disappearing fluids, or is this simply the symptom of an a high mileage motor? Normally I wouldn't be concerned about the oil consumption in an older rig, but the addition of the disappearing coolant has me wondering. I've driven and kept up on high mileage vehicles all my life, and the coolant thing is a new one on me with no apparent leaks. I don't have access to a pressure tester, so unfortunately I can't help there.

Any help, advice or experience is greatly appreciated

At 12 years old and 275K, she's due for new coolant tees at the firewall heater hose connections. They often start to signal they're failing by cracking slightly and seeping coolant. You can run your fingers under them when the engine is cold and check for coolant residue. Either way, it's past due if they haven't been done already, and if they fail, you're on the side of the road with an overheated engine after all of the coolant got pumped onto the highway over about 10 seconds.

You'll need these to do the job:

More Information for DORMAN 626553

More Information for DORMAN 800413

More Information for DORMAN 800414

Plus some heater hose, appropriate spring clamps, and coolant. Early versions of the Dorman brand tees had a poor reputation, but I've found more recent versions to hold up just fine. The Dorman brand hose I linked has a metal wye in it, so it's preferred over the factory part.

I would also be looking at the radiator end tanks. With that mileage, the radiator is also likely due and probably seeping through micro cracks. And if you have the coolant tees out, you might as well replace the radiator, water pump, thermostat and hoses, too. Chances are this will solve all of your coolant loss problems, unless it's a head gasket, which isn't common on these. I consider these items normal maintenance on these trucks, so I did them proactively on both of my Yukon XL's.

 

[the blur]

I just went through this on my 6.2L motor. monthly top off of coolant. It's a radiator. Finally got bad enough to find it.

 

[West 1]

I had an Escalade doing this. Leak was found to be in the rear, passenger side where the heater hoses connect tot he rear AC and Heat.
With your miles I would have the radiator tested for Hydro carbons, you can also buy a kit at any local parts store to do this. If the kit finds hydrocarbons in your radiator the head gaskets are leaking, if not they are good. Quick and pretty cheap test to rule it out. I lean towards this since your idle is fluctuating, the engine is compensating for something.

 

[lifeisamystery]

Yeah, we happened to see my radiator do it on a fluke while we were re-doing the front end. It didn't seep for very long, a few seconds at most and then it stopped. Looks like a hairline crack in the plastic end cap on the driver's side. Seriously debating on taking the $300 hit to replace it with an all metal one. Are the new "OEM" plastic ones just as crappy?

 

[West 1]

If it went 250,000 miles I would rate it as really good not crappy.

 

[Doubeleive]

Yeah, we happened to see my radiator do it on a fluke while we were re-doing the front end. It didn't seep for very long, a few seconds at most and then it stopped. Looks like a hairline crack in the plastic end cap on the driver's side. Seriously debating on taking the $300 hit to replace it with an all metal one. Are the new "OEM" plastic ones just as crappy?

oem is your best option.
coolant only goes 2 places
it either leaks out, or leaks in
sounds like you got lucky and found where it is leaking out

 

[the blur]

This forum is funny. The GM plastic radiator goes for 10 years, and the forum calls it junk, get metal.
The hydraulic motor mounts go for 80,000 miles, and the forum calls it junk, go for solid mounts.
OK, let's defeat 10 zillion dollars of GM engineering.

 

[Fless]

This forum is funny. The GM plastic radiator goes for 10 years, and the forum calls it junk, get metal.
The hydraulic motor mounts go for 80,000 miles, and the forum calls it junk, go for solid mounts.
OK, let's defeat 10 zillion dollars of GM engineering.

I have to say that I have seen more comments saying to get OEM than recommending the all-aluminum radiators that tend to leak. Maybe you're not seeing the same posts.

 

[j91z28d1]

This forum is funny. The GM plastic radiator goes for 10 years, and the forum calls it junk, get metal.
The hydraulic motor mounts go for 80,000 miles, and the forum calls it junk, go for solid mounts.
OK, let's defeat 10 zillion dollars of GM engineering.

literally no one recommends aluminum radiators here. there's a DENSO everyone runs.

a motor mount that only lasts 80k miles is junk. they should last the life of the car.

 

[lifeisamystery]

literally no one recommends aluminum radiators here. there's a DENSO everyone runs.

a motor mount that only lasts 80k miles is junk. they should last the life of the car.

The only reason I even asked about the all aluminum radiators because I've literally never had to replace one before and the very last time I ever even heard of anyone replacing one was back when they were all metal LOL

 

[j91z28d1]

The only reason I even asked about the all aluminum radiators because I've literally never had to replace one before and the very last time I ever even heard of anyone replacing one was back when they were all metal LOL

yeah, not you, the other guy that seems to be misunderstanding. what's commonly recommended here.


in general I've always had good luck with replacing stock plastic radiators with aftermarket aluminum ones in performance cars that need extra cooling, but it seems the ones for these trucks aren't very good and crack over time. the pic I saw the weld quality didn't look great. so for the price and guys towing way over the ratings seem to cool fine with the cheaper DENSO. so it's the standard recommendation around here.

 

[Grady_Wilson]

My Yukon was losing radiator fluid over time and it did not appear to be leaking anywhere at all.
When I replaced the Ts on the firewall, it was clear that one had a slight leak that never made it to the garage or driveway floor.
When working on everything I did notice a very slight corrosion on one of the mounting bolts for the rear coil pack directly under the Ts.
There was never any evidence of leakage, anywhere, but it was losing fluid over time.
Now that the Ts have been replaced along with a bunch of hoses, there is zero fluid loss.